The present invention relates to an electronic device.
JP-A-2-272737 discloses technology that forms a resin protrusion on an active surface of a semiconductor chip, and forms an interconnect from an electrode on the active surface to extend over the resin protrusion to form a bump electrode. According to this technology, stress can be reduced by the resin protrusion while providing the bump electrodes at a pitch and an arrangement differing from those of the electrodes. Japanese Patent No. 2744476 discloses technology that mounts a semiconductor device having bump electrodes on a wiring board utilizing an electrically insulating adhesive. When the semiconductor device is mounted on the circuit board, a resin protrusion under the bump electrode is compressed between the semiconductor chip and the wiring board, and an interconnect of the bump electrode comes in contact with a wiring pattern of the wiring board under pressure due to the elasticity of the resin protrusion. This enables the bump electrode and the wiring pattern to be stably connected even if the bump electrodes formed on the semiconductor chip differ in height or the substrate is warped.
Japanese Patent No. 2731471 discloses a structure in which an adhesive and a resin protrusion have an identical coefficient of linear expansion. However, the structure disclosed in Japanese Patent No. 2731471 is not suitable for practical applications since only limited materials can be used. JP-A-2005-101527 discloses technology that maintains the compressed state of a resin protrusion when an adhesive expands due to heat, even if the coefficient of linear expansion of the resin protrusion is greater than that of the adhesive, by compressing the resin protrusion to an extent greater than the difference in the amount of expansion between the resin protrusion and the adhesive when the resin protrusion and the adhesive are heated, thereby maintaining electrical connection utilizing the bump electrode.
However, since the glass transition temperature of the adhesive is lower than that of the resin protrusion, the adhesive softens earlier than the resin protrusion. In this case, the compressed resin protrusion expands due to the thermal expansion of the resin protrusion and the repulsive force against compression. Therefore, the resin protrusion almost completely recovers its original shape so that the pressure contact state of the resin protrusion cannot be maintained. This makes it impossible to ensure electrical connection.